Continuous flow-constructed wetlands for the treatment of swine waste water

Authors: Ibekwe, Abasiofiok - Mark; MURINDA, SHELTON - California Polytechnic State University

Submitted to: International Journal of Environmental Research and Public Health
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 6/27/2018
Publication Date: 6/29/2018
Citation: Ibekwe, A.M., Murinda, S.E. 2018. Continuous flow-constructed wetlands for the treatment of swine waste water. International Journal of Environmental Research and Public Health. 15(7):1369. https://doi.org/10.3390/ijerph15071369.
DOI: https://doi.org/10.3390/ijerph15071369

Interpretive Summary: The treatment and removal of contaminants from swine waste water by continuous flow constructed wetland involves complex biological, physical, and chemical processes that may produce better quality water with reduced levels of contaminants for different end-users. Constructed wetlands can offer these benefits such as water-quality improvement, water reclamation, habitat for species conservation, flood control, recreational and education activities for human populations in both developed and developing countries. In the swine production system, wastes are traditionally flushed into an anaerobic lagoon and then sprayed on agricultural fields. The lagoon and spray field system is the most commonly used method to dispose of liquid waste from swine houses. In this study, a continuous flow constructed wetland was used to remove contaminants from swine waste. We determined population structure and genetic diversity of E. coli from the swine house through a continuous flow constructed wetland used for treatment and removal of contaminants in swine waste. E. coli isolates identified from this study did not contain E. coli O157. However, a few non O157 E. coli and other types of E. coli that may be responsible for travelers’ diarrhea were identified. This information will be of interest to swine farmers, water quality agencies, government agencies, and researchers.

Technical Abstract: The microbiological quality of treated waste water is always a concern when waste water is disposed to the environment. However, when treated appropriately, such water can serve many purposes to the general population. Therefore, the treatment and removal of contaminants from swine waste water by continuous flow-constructed wetlands involves complex biological, physical, and chemical processes that may produce better quality water with reduced levels of contaminants. Swine waste contains E. coli populations and other bacterial contaminants originating from swine houses through constructed wetlands, but little is known about E. coli population in swine waste water. To assess the impacts of seasonal variations and the effect of the wetland layout/operations on water quality, E. coli isolates were compared for genetic diversity using repetitive extragenic palindromic polymerase chain reaction (REP-PCR). None of the isolates was confirmed as Shiga toxin producing E. coli O157:H7 (STEC); however, other pathotypes, such as enterotoxigenic E. coli (ETEC) were identified. Using a 90% similarity index from REP-PCR, 69 genotypes out of 421 E. coli isolates were found. Our data showed that the E. coli population was significantly (p = 0.036) higher in November than in March and August in most of the wetland cells. Furthermore, there was a significant (p = 0.001) reduction in E. coli populations from wetland influent to the final effluent. Therefore, the use of continuous flow-constructed wetlands may be a good treatment approach for reducing contaminants from different waste water sources.